Clips going out of sync, phase randomly flipping?

[ClarkPlaysGuitar]

I have one song that is doing weird things while working on the mix. There are some harmony guitar lines that occur in 3 or 4 places during the song, which I just punched in at the appropriate spot. Occasionally they will go out of sync with the other tracks during playback. The first time I heard it I thought I had played them way out of time & kind of freaked, because I was certain I had nailed them during recording. But when I went back to re-listen, they were okay.  It happens about every 5th or 6th time I play the song back, and it is not all of the harmony lines, just the ones before the guitar solo.  The other places they occur in the song never seem to go out of sync.

The other odd thing on this tune is the bass tracks going out of phase randomly. I fed the bass to 2 separate tracks during recording, each with a distinct sound. Near the end of the song there is a split in the clips where I went to an alternate take for the last part of the song. Where the split occurs the two bass tracks will randomly go out of phase during playback. This does not happen on every playback, just occasionally. When it does happen I can flip the phase on one of the tracks while it is still playing, and it will sound right for a few measures, then it suddenly sounds out of phase again, so I flip it back and it's ok.        

So far, when I export the test mixes to a stereo wave file none of these anomalies occur on the tune, so it may not be worth getting worked up about. I am curious if anyone else has had similar issues, and if so, did you find a cause and/or a solution?

Thanks for your thoughts!

[David Baay]

Does it happen if you play the whole thing through from the start without interruption or looping?

My first guess would be some plugin has unsynced randomness in realtime that does not occur (or occurs less frequently) with offline rendering.

You might try bypassing some FX to determine the culprit, and then Google for similar reports on the web at large or the vendor's forum for possible solutions.

You migth also experiment with different ASIO buffer sizes, and see if maybe that's a factor. If you have a non-zero bouncebuffsizemsec=  parameter value specified in AUD.INI that's different from your real-time buffer size, that might explain why the issue doesn't manifest when exporting.

 

 

[bitflipper]

That was my first thought, too - that a defective plugin might be causing the phase shift. But if the polarity reversal actually shows up as such in the phase button's icon, well, a plugin can't do that. I'd start with a global fx bypass and play the song "5 or 6 times" to verify that it's an effect that's causing the shift. If the problem goes away, start eliminating the types of plugins that affect phase - a tape echo, phaser, chorus, flanger or delay would be logical candidates.

[ClarkPlaysGuitar]

Thanks for the thoughts, guys. Bitflipper, the phase issue doesn't actually show up on the icon, there is just a sudden drop in volume and a change in sound. My initial thought was that I had inadvertently moved one of the bass clips a tiny bit, causing it to be out of phase, but that wasn't it, I'll play around with the FX & see what results I get.

So far this phenomenon has not shown up on other songs from the same session, using mostly the same plugins, but I will have to dig in to see if I did pop some plugin onto a channel in this track that I'm not using on the other tunes.

As always, this forum delivers! Thank you both so much!

 

[ClarkPlaysGuitar]

Well, here's the update, but there is not much to tell. It took some time because of having to replay the song at least 6 times with each "experiment." 

First thing I tried was turning off all of the FX, and as suspected, neither the faux-phase-flipping nor the out-of-sync guitar phrases occurred. Then I began the process of adding the plugins back in, one at a time. I got maybe two added back in before I ran out of time that day. Over the the course of a few days I tried each plugin individually, and did not experience either of the issues. So I concluded that it was being caused by a combination of plugins, but which ones?

I tried a couple variations with no results. Then I saw there was a new update for CbB, so I installed it. I have not been able to replicate the issue since, so I guess we can call this solved.

Thanks again for the thoughts & suggestions.

[David Baay]

Good to hear. All's well that ends well, right?